A conventional machine for installing mine roof bolts uses bolts of a fixed length and requires a considerable amount of head room. For a thick mineral vein which it is desired to mine in several passes of the mining equipment, the mine roof must be rebolted before each pass.
Pultruded continuous fiber reinforced plastic mine roof bolts are disclosed in U.S. Pat. Nos. 4,194,873 and 4,247,224.